The present invention relates to a control method for channel assignment with respect to a communication apparatus (base station) that processes data communicated through a plurality of channels. More particularly, the present invention relates to a communication apparatus suitably employable for a mobile communication system operated with use of a CDMA (Code Division Multiple Access) method.
In recent years, there has been a demand for mobile communications of various information transmission services, such as large capacity fast data communications of dynamic pictures, etc. in addition to conventional voice and data communications. In order to meet such a variety of service demands from many users, each base station is required to have a signal processing unit composed of a huge size circuit.
FIG. 1 shows a configuration of such a conventional base station used for a CDMA mobile communication system. In this case, voice communications are represented as low speed data rate communication services and data communications are represented as high speed data rate communication services. Although both voice communications and data communications are described below, communication services are not limited only to those communications; they are just picked up so as to denote that a base station is required to support a plurality of communication services supplied at different transmission rates.
A carrier frequency band signal received by an antenna 100 is converted to a base band received signal in an RF (Radio Frequency) unit 101, and then it is supplied to a base band unit 134. Each channel base band signal output from the base band unit 134 is superimposed with others in an output combination unit 107, and then is converted to a carrier frequency band signal and transmitted from the antenna 100.
In the base band unit 134, modem processing units 102-1 to 102-s are provided in accordance with the number of channels (s) used in the base station. Each modem processing unit 102 is used to transmit/receive signals of one channel. A matched filter (NW) 135 and a peak detector 136 are provided for a group of channels, respectively, so that path searching is done in each channel intermittently. The peak detector 136 selects a larger correlation value (denoting a multi-path receiving timing) of correlation values output from the MF. The selected path timing is set for a correlator 108-1 to n(n: number of fingers) of a modem processing unit 102-1 to 102-s of the corresponding channel so as to carry out a despreading processing for each finger.
In each base station, path searching is done for each channel periodically in a time sharing manner as described above. Consequently, an MF can be shared by a plurality of channels, thereby the system circuit is reduced in size. Even in this case, however, because each channel is provided with a modem processing unit 102, as many modem processing units 102 must be provided as the number of users in the system.
Furthermore, for a high speed user transmission rate, each block operation must be speeded up, and, accordingly, the circuitry is expanded in size, although the block configuration of the modem processing unit 102 remains the same.
If a base station supports both voice and high speed data communication services, the modem processing unit 102 provided for each channel is roughly classified into the following two configuration types.
One of the two types is a configuration in which as many of the modem processing units for voice 201-1 to 201-i and the modem processing units for high speed data communications 202-1 to 201-j in the base band unit 134 shown in FIG. 2 are provided as the number of system-supported users. The number of users for high speed data communications is more than the number of users for voice communications. However, because the transmission rate is high, the processing block circuit size for high speed data communications comes to be larger than that for voice communications.
The other type configuration is as shown in FIG. 3, wherein as many of the high performance modem processing units for voice/data communications 301 are provided as the number of system-supported users (301-1 to k), so that both voice and data communications are processed in a common processing block. The inner configuration of the base band unit 134 is only a difference between FIG. 2 and FIG. 3. The configurations of the RF unit 101, the output combination unit 107, and other components in FIG. 3 are the same as those in FIG. 2.